Process for the reaction and absorption of gaseous air pollutants, apparatus therefor and method of making the same

ABSTRACT

A method of decreasing the level of NOx, CO and SO 2  emissions in a gas turbine is disclosed. A catalyst absorber, preferably made of alumina/platinum/carbonate salt, is used to oxidize the pollutant oxides and absorb them. The catalyst absorber can then be regenerated and reused. An apparatus for treating the stack gases, and a method of making the catalyst absorber are also described.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a process for reducing gaseouspollutants in the air, namely nitrogen oxides (NOx), sulfur oxidesand/or carbon monoxide (CO), which are produced by combustion ofhydrocarbons or hydrogen in an engine or boiler, and primarily, in a gasturbine. The present invention is also directed to an apparatus forperforming the process and a process for making the reactor/catalystabsorber.

2. Art Background

Turbine power plants are becoming the standard for generatingelectricity because they are so efficient compared to any other form ofpower manufacture. Turbine power plants that burn methane to producepower for residents and manufacturing facilities in cities also producecarbon monoxide and nitrogen oxide as pollutants. It is highly desirableto reduce or eliminate these pollutants so that the air is notcontaminated as a result of power production.

Initially, the permitted level of pollution by power plants for nitrogenoxides (NOx), which includes nitric oxide (NO) and nitrogen dioxide(NO₂), was less than 100 parts-per-million (ppm) and the level of carbonmonoxide (CO) was to a level of less than 100 ppm. Later, a second stepwas taken to reduce the NOx to less than 25 ppm and the CO today isstill permitted at any amount less than 100 ppm. Using currenttechnology, the output levels of NOx can be reduced to the range of 5 to9 ppm plus NH₃ slippage resulting from the selective catalytic reduction(SCR) technology described below.

The only technology which is currently available to obtain the 5-9 ppmNOx levels is called selective catalytic reduction, in which ammonia ismixed with the flue gas and then passed over a catalyst whichselectively combines the nitrogen oxides and ammonia to eliminate amajor portion of the NOx. One problem with the selective catalyticreduction is that as a practical matter, it is only capable of reducingthe NOx to the range of 5 to 9 ppm. Another problem, referred to asslippage, is caused by hazardous ammonia passing through the catalyst.

Another problem of the SCR technology is that the operating conditionsrequired for SCR are only achieved by expensive modifications of thedown stream boiler or heat exchanger system.

There have been other technologies for reduction of pollution which havebeen advanced, such as overwatering in the combustor, and these alsohave the potential to reduce the NOx pollution, but none of them reducethe NOx to levels much less than 5 to 9 ppm.

In a copending application owned by the assignee of the presentapplication, a system comprising essentially a two step process has beendescribed. In the first step, the stack gases are first contacted with acatalyst under certain conditions which cause the oxidation of certainoxide pollutants, including NO and CO. In the second step, the oxidizedpollutants are absorbed in an absorption bed.

It would be desirable to combine the oxidation and absorption steps intoa single step performed by a single material.

SUMMARY OF THE INVENTION

The present invention has the capability of reducing hydrocarbon burningengine waste pollutants, and particularly those from a gas turbine,including nitrogen oxide, carbon monoxide and sulfur oxides. Theinvention, as described in more detail below, includes a novel catalyticabsorber and method of making the absorber, a novel process andapparatus capable of reducing air pollutants and the method of makingthe apparatus.

The pollutants from a turbine in a power generating stack are primarilypresent as NO. The process of the present invention causes oxidation ofthe NO to NO₂. This produces NO₂ from substantially all of the nitrogenoxides (NO). NO₂ is a much more active material and can be and isabsorbed readily by the catalytic absorber from the gas stream even whenpresent at low concentrations in the ppm range.

The turbine exhaust gases are initially at about 1000° F. after theshaft energy has been withdrawn from them. These gases are then passedover heat exchangers to remove energy and produce steam while coolingthe exhaust or stack gases. Stack gases are moving at high velocitydepending upon the diameter of the stack, and after heat is removed, thestack gases typically are in the range of 250° to 500° F. and travelabout 30-50 feet per second. The gas contains 13-15% oxygen, up to about12% water, and about 4% carbon dioxide. This is in addition to thepollutants, which are the NOx mixed with approximately 90% NO and 10%NO₂, CO in the range of 30 to 200 ppm and sulfur dioxide (SO₂) in therange of about 0.2 to 2.0 ppm when natural gas is the fuel.

The present invention involves a one step/one element process andapparatus to remove the nitrogen oxides, carbon monoxide, and sulfuroxides from the stack gases. Using a combined catalyst/absorber, thenitrogen oxides are oxidized to nitrogen dioxide; the carbon monoxidesare oxidized to carbon dioxide, and the sulfur dioxide (SO₂) is oxidizedto sulfur trioxide (SO₃). This oxidation occurs at temperatures in therange of 150° to about 425° F. and more preferably in the range of 175°to 400° F., and most preferably in the range of 200° to 365° F. Thespace velocity of the exhaust gas may be in the range of 5,000 to 50,000per hour and more preferably in the range of 10,000 to 20,000 per hour,although it is anticipated that a larger range will permit effectiveoperation without an undue reduction in quality of the output gas. Asused herein, the term space velocity means volume units of flow pervolume units of catalyst per hour.

The catalyst absorber of the present invention absorbs the oxidizedoxides so that only a small percentage, generally 10% or less of theinitial oxide pollutants, pass through the system and are released.While not being bound to a particular theory, it is presently believedthat the reactions which occur are as follows for each of the threepollutants, with an oxidation occurring, followed by a reaction with thecarbonate such as Na₂ CO₃ : ##STR1##

The catalyst/absorber may be a platinum catalyst supported on aluminawith an alkali or alkaline earth carbonate or bicarbonate coatingthereon, the carbonate coating being lithium, sodium, potassium orcalcium carbonate, and presently the preferred coating is a potassiumcarbonate.

The absorber, when it ceases to be effective, and specifically, when thelevel of pollutants emanating from the apparatus after contact with thecatalyst absorber increases beyond an acceptable level, can be replaced,and the used absorber can be recharged to an effective status again.Recharging of the catalyst is accomplished by removing the spent(saturated or partially saturated) carbonate and replacing the spentcarbonate with fresh unreacted carbonate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic depiction of the catalyst absorber of the presentinvention.

FIG. 1a is a drawing of a catalyst absorber sphere in a preferredembodiment.

FIG. 1b is a magnefied drawing of a portion of the surface of thecatalyst absorber sphere of the present invention.

FIG. 1c is a drawing of the surface of a monolith catalyst absorber ofthe present invention.

FIG. 2 is a flowchart showing the process of making the catalyst of thepresent invention.

FIG. 3 is an illustration of a wheel apparatus for changing andregenerating the oxidation catalyst/absorber of the present invention.

FIG. 4 is an illustration of a carousel apparatus for changing andregenerating the oxidation catalyst/absorber of the present invention.

FIG. 5 is an illustration of a fluidized bed apparatus for changing andregenerating the oxidation catalyst/absorber of the present invention.

FIG. 6 is an illustration of a multiple fluidized bed apparatus forchanging and regenerating the oxidation catalyst/absorber of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a material for removing gaseouspollutants from combustion exhaust streams, in which the materialcomprises an oxidation catalyst specie disposed on a high surface areasupport coated with an absorber material. The oxidation catalyst specieis selected from the group of noble metal elements, base metaltransitional elements and combinations thereof. More particularly, theoxidation catalyst species are selected from platinum, palladium,rhodium, cobalt, nickel, iron, copper and molybdenum, and preferably,platinum and rhodium, and most preferably, platinum.

The oxidation catalyst specie concentration is 0.05 to 0.6 percent byweight of the material, and preferably is 0.1 to 0.4 percent by weightof the material, and most preferably is 0.15 to 0.3 percent by weight ofthe material. More than one element may be used as an oxidation catalystspecie, and under these conditions each of said elements has aconcentration in the range of 0.05 to 0.6 percent by weight.

The high surface area support is made of alumina, zirconia, titania,silica or a combination of two or more of these oxides. Preferably, thehigh surface area support is made of alumina. The surface area of thesupport is in the range of 50 to 350 square meters per gram, preferably100 to 325 square meters per gram, and more preferably 200 to 300 squaremeters per gram. The high surface area support may be coated on aceramic or metal matrix structure.

The catalyst absorber may be in a shape such as a sphere, solidcylinder, hollow cylinder, star shape or wheel shape.

The absorber is coated with at least one alkali or alkaline earthcompound, which can be a hydroxide compound, bicarbonate compound, orcarbonate compound, or mixtures of hydroxides and/or bicarbonates and/orcarbonated compounds. Preferably, the absorber comprises substantiallyall carbonate, and most preferably sodium carbonate, potassium carbonateor calcium carbonate. The absorber is disposed on the material at aconcentration in the range of 0.5 to 20 percent by weight of thematerial, preferably 5.0 to 15 percent by weight of the material, andmost preferably about 10% percent by weight of the material.

The process for making the novel catalyst absorber of the presentinvention includes applying the oxidation catalyst specie from solution.The solution is preferably a nonaqueous solution. The oxidation catalystspecie may also be applied from chloride free aqueous solution. Onceapplied the oxidation catalyst specie is dried after application and maybe activated after application, possibly by calcining it.

After the catalyst absorber is spent or partially spent, it can bereactivated. Reactivation is accomplished by removing and replacing thespent absorber and disposing of the removed spent absorber. The spentabsorber can be used as fertilizer in that it is rich in nitrogen,carbon and sulfur. Alternatively, reactivation is accomplished bydecomposing components formed by the combination of pollutants with theabsorber and trapping the concentrated pollution gases for disposal oruse. The apparatus of the present invention supports the catalystabsorber and contacts the catalyst absorber with a combustion exhaust.It includes a means for removing spent catalyst absorber from contactwith the combustion gases and at the same time moving an equivalentamount of new or regenerated catalyst absorber into contact with thecombustion gas to maintain a specified outlet pollution concentrationlimit. The apparatus is in the shape of a wheel or carrousel, or it maybe a fluid bed or two or more beds which are alternately used forabsorption of pollutant gases and reactivated.

As shown in FIG. 1, the catalyst absorber of the present invention cantake on different configurations. FIG. 1a shows a spherical catalystabsorber made up of an alumina sphere 10 with a platinum coating 12 anda carbonate coating 14 thereon. As shown in FIG. 1b, the surface of thesphere is very irregular so that there is an extremely large surfacearea per gram of material as described herein. As shown in FIG. 1c, thecatalyst absorber can be in the form of a monolith surface including aceramic or stainless steel support 20, an alumina layer 22, a platinumlayer 24 and a carbonate layer 26.

The method of making the catalyst absorber is shown in FIG. 2. Thecatalyst/absorber of the present invention is made by starting with highsurface area alumina spheres having a surface area of 50 to 350 squaremeters per gram, these spheres being commercially available from severalsources, and preferably from La Roche Chemicals, Inc., Baton Rouge, La.The spheres are approximately 1/8 inch in diameter. It will beappreciated that other forms of supports may be used without from thespirit and scope of the present invention. The alumina spheres arewashed with distilled water to remove small particles bound loosely tothe surface. The spheres are then dried for about 16 hours at 300° F. toensure that all of the cavities and interstices in the spheres are fullydried, and that the surface is free of water. The spheres are thenstored in an air-tight container until ready for further processing.

A solution of Pt 2-ethylhexanoate which contained 25% Pt was added totoluene to get a concentration of Pt such that the weight of solutionequal to the toluene uptake would contain sufficient Pt to give aloading of 0.23 weight percent per weight of alumina. The platinumcoated spheres were then dried for 1 hour at 900° F. in air. The spheresare then cooled to approximately room temperature and stored in anair-tight container again. The platinum coated spheres are then coatedwith an alkali or alkaline earth carbonate or bicarbonate coating, thealkali or alkaline earth carbonate or bicarbonate being selected fromlithium, sodium, potassium or calcium carbonate or bicarbonate solution,preferably, a sodium carbonate solution at a concentration of 14 percentby weight in distilled water. The water was heated to dissolve all ofthe sodium carbonate. The carbonate coated spheres were then dried at300° F. for two hours. The final catalyst absorber had a coating ofplatinum in the amount of 0.23 weight percent added to the alumina, and10.0 weight percent Na₂ CO₃ added to the alumina. The spheres are thendisposed in a 3×3×6 inch wire mesh basket and used as described below.

Alternatively, another form of the catalyst absorber can be made usingceramic or metal monolith supports. Tests were performed by taking acore plug of a metal monolith having approximately 300 openings persquare inch, obtaining a core from the monolith of appropriatedimensions for use in the test equipment, coating the surface of thechannels in the monolith with alumina from a water slurry, calcining at900° F. or 3 hours, and cooling. This core is then coated with aplatinum coating as described above with respect to the spheres and thenthe carbonate is applied by the method used for the spheres.

After the catalyst absorber is exhausted or saturated, it can beregenerated. A typical regeneration procedure is as follows:

1. The beads after cooling are transferred to containers approximately7"×10"×5". The containers have closeable lids and inlet and outlet gasor drain lines.

2. Approximately 260 cubic inches of spheres are washed at 190° F. with4 liters of demineralied water for five minutes with stirring.

3. Samples are taken as the liquid is drained off.

4. Three liters of approximately 14% sodium or potassium carbonatesolution at 190° F. are added to the container.

5. The spheres are stirred and soaked for 20 minutes, or as little as 2to 5 minutes.

6. Samples are taken as solution is drained.

7. In a 300° F. furnace the beads are dried for 45 minutes withapproximately 10 scfm heated dry air flowing through the container.

8. The weighed dry Lads are returned to the screen container for reuse.

As shown in FIG. 3, the catalyst absorber of the present invention canbe installed in a wheel apparatus to permit contacting stack gases withthe catalyst absorber and regenerating the catalyst absorber after it issaturated or partially saturated. As shown in FIG. 3, the wheelapparatus includes an inlet 30 for receiving the combustion gases andstack 32 for exhausting the treated gases, a cylindrical assembly 34containing catalyst absorber and a regenerating unit 36 for regeneratingthe spent catalyst, the regenerating unit having an inlet 37 and outlet38 for replenishing fresh regeneration fluid. The inner wall 39 andouter wall 40 of a portion of the wheel adjacent the stack 32 areperforated or otherwise vented to permit passage of the gastherethrough. The inner and/or outer walls 41 and 42 of the remainder ofthe wheel is closed so that the exhaust gases only exhaust through thestack 32. A drive 44 is used to rotate the wheel either discretely orcontinuously. Arrow A designates the direction of the drive 44 roatationand arrow B indicates the direction of the wheel rotation.

As shown in FIG. 4, an alternative arrangement for the catalyst adsorberis disclosed, in which a carousel is used. The stack gases enter throughthe inlet 50 and exit through the stack 52. The catalyst absorber isinserted in line with the stack gases at 54, and when spent is retractedinto the carousel at 56 and a new absorber installed. The spent catalystabsorber is then regenerated. Fresh regeneration fluid enters throughinlet 57 and is remove through outlet 58.

As shown in FIG. 5, a fluidized bed apparatus is disclosed. Thisapparatus has a combustion gas inlet 60 and stack outlet 70. There is afluidized bed 62 in line with the gas which contains active catalystabsorber. A portion of the catalyst absorber is removed from thefluidized bed and moved to the regeneration unit 64. Regeneration fluidis sent into the regenerator at 65 and is removed by the fluid separator66.

As shown in FIG. 6, a multiple fluidized bed apparatus is disclosed.This apparatus has a combustion gas inlet 71 and stack outlet 80. Thereis a first fluidized bed 72 in line with the gas which contains activecatalyst absorber. There is a second fluidized bed 73 which is beingregenerated. The first fluidized bed has inlet 76 and outlet 77 withvalves to permit regeneration fluid in and out. The second fluidized bedhas inlet 74 and outlet 75 with valves to permit regeneration fluid inand out. Valve 78 controls whether combustion gases go to the first orsecond fluidized bed.

In the following examples, gas measurements were made as follows: CO wasmeasured by a TECO model 48 infrared analyzer, CO₂ was measured by aHoriba CO₂ infrared meter and NO and NO₂ were measured using a TECOmodel #10R chemiluminescent detector with a stainless steel converter.Sulfur oxides were measured using a TECO model #43a Pulsed FluorescenceSO₂ Analyzer.

Examples of the performance of the present invention are set forthbelow.

Experiment No. 1

In each of the following experiments, the starting gas was obtained froma slip stream from the turbine exhaust from a cogeneration plantturbine. The catalyst absorber was disposed in two wire mesh basketshaving a 3 inch by 3 inch by 6 inch geometry and placed in line with theslip stream in series to minimize any edge effects and ensure that allof the slip stream comes in contact with the catalyst absorber. Thespace velocity of the slip stream was 18,000 per hour. The twotemperatures listed indicate the temperature for the upstream firstbasket and the temperature for the downstream second basket. Allpollutant measurements are in ppm. NOx is the total concentration ofnitrogen oxide (NO) and nitrogen dioxide (NO₂).

    ______________________________________                                        Initial Starting Pollutant Levels                                             CO in, 10.98 ppm                                                              NO in, 29.0 ppm                                                               NOx in, 33.0 ppm                                                              Time     Temp 1   Temp 2   CO out                                                                              NO out NOx out                               Hours: Min.                                                                            (°F.)                                                                           (°F.)                                                                           (ppm) (ppm)  (ppm)                                 ______________________________________                                        :15      230      216      0.36  3.0    3.0                                   :30      355      323      0.18  3.0    4.0                                   :45      355      328      0.20  3.0    4.0                                   1 hour   354      329      0.19  3.0    5.0                                   1:15     352      328      0.20  3.0    5.0                                   1:30     351      328      0.23  2.5    6.0                                   1:45     350      327      0.25  3.0    7.0                                   2 hours  348      325      0.17  7.0    8.0                                   2:15     348      325      0.17  7.0    8.0                                   2:30     348      325      0.19  8.0    10.0                                  2:45     348      325      0.18  9.0    10.0                                  3 hours  348      325      0.18  10.0   11.0                                  3:15     347      3251     0.17  11.0   12.0                                  3:30     346      323      0.17  11.0   12.0                                  3:45     346      322      0.18  12.0   13.0                                  ______________________________________                                    

Experiment No.1-a

The catalyst absorber was regenerated, and the experiment was run againunder the same conditions, using the regenerated catalyst absorber.

    ______________________________________                                        Initial Starting Pollutant Levels                                             CO in, 9.91 ppm                                                               NO in, 30.0 ppm                                                               NOx in, 36.0 ppm                                                              Time     Temp 1   Temp 2   CO out                                                                              NO out NOx out                               Hours: Min.                                                                            (°F.)                                                                           (°F.)                                                                           (ppm) (ppm)  (ppm)                                 ______________________________________                                        :15      135      162      2.49  16.0   16.0                                  :30      365      160      .13   5.0    5.0                                   :45      363      351      .05   2.0    2.0                                   1 hour   363      353      .05   2.5    2.5                                   1:15     362      353      .08   4.0    4.0                                   1:30     362      352      .05   4.5    5.0                                   1:45     362      354      .07   5.5    6.0                                   2 hours  362      354      .07   6.0    7.0                                   2:15     362      354      .07   7.0    8.0                                   2:30     361      353      .06   7.5    8.5                                   2:45     362      354      .09   8.5    9.5                                   3 hours  362      354      .08   9.0    10.0                                  3:15     362      354      .08   9.0    10.5                                  3:30     363      355      .08   10.0   11.5                                  3:45     363      356      .08   10.0   12.0                                  4 hours  364      356      .07   10.5   12.5                                  ______________________________________                                    

It is believed that the first reading at 15 minutes showed highpollution level because the temperature of the catalyst absorber wasbelow the necessary temperature for oxidation.

Experiment No. 1-b

The catalyst absorber was regenerated a second time, and the experimentwas run again under the same conditions, using the twice regeneratedcatalyst absorber.

    ______________________________________                                        Initial Starting Pollutant Levels                                             CO in, 13.16 ppm                                                              NO in, 26.0 ppm                                                               NOx in, 32.5 ppm                                                              Time     Temp 1   Temp 2   CO out                                                                              NO out NOx out                               Hours: Min.                                                                            (°F.)                                                                           (°F.)                                                                           (ppm) (ppm)  (ppm)                                 ______________________________________                                        :15      133      134      0.2   23.0   23.0                                  :30      296      139      3.02  16.0   16.0                                  :45      331      142      0.43  7.5    7.5                                   1 hour   296      296      0.30  6.0    6.0                                   1:15     285      285      0.34  7.0    7.0                                   1:30     279      278      0.37  8.5    8.5                                   1:45     282      273      0.40  10.0   10.0                                  2 hours  304      290      0.30  9.5    9.5                                   2:15     320      308      0.25  9.5    10.0                                  2:30     330      319      0.22  10.0   11.0                                  2:45     339      329      0.20  10.5   12.0                                  3 hours  343      334      0.20  11.5   12.5                                  3:15     347      338      0.22  12.0   14.0                                  ______________________________________                                    

Experiment No. 1-c

The catalyst absorber was regenerated again, and the experiment was runagain under the same conditions, using the three time regeneratedcatalyst absorber.

    ______________________________________                                        Initial Starting Pollutant Levels                                             CO in, 12.13 ppm                                                              NO in, 28.0 ppm                                                               NOx in, 34.0 ppm                                                              Time     Temp 1   Temp 2   CO out                                                                              NO out NOx out                               Hours: Min.                                                                            (°F.)                                                                           (°F.)                                                                           (ppm) (ppm)  (ppm)                                 ______________________________________                                        :15      142      155      7.61  20.0   20.0                                  :30      352      195      0.30  3.0    3.0                                   :45      350      342      0.22  2.5    2.5                                   1 hour   351      342      .23   3.0    3.5                                   1:15     351      343      0.24  4.0    4.5                                   1:30     351      345      0.24  5.0    5.5                                   1:45     351      344      0.27  6.0    6.5                                   2 hours  352      345      0.24  6.5    7.5                                   2:15     351      346      0.24  8.0    9.0                                   2:30     351      345      0.23  8.0    9.0                                   2:45     351      345      0.30  9.0    10.0                                  3 hours  350      343      0.37  9.5    11.0                                  3:15     350      342      0.28  10.0   12.0                                  3:30     348      341      0.30  11.0   12.0                                  3:45 348 341      0.30 12.0                                                                              13.5                                               ______________________________________                                    

Experiment No. 1-d

The catalyst absorber was regenerated again, and the experiment was runagain under the same conditions, using the four time regeneratedcatalyst absorber.

    ______________________________________                                        Initial Starting Pollutant Levels                                             CO in, 13.6 ppm                                                               NO in, 28.0 ppm                                                               NOx in, 34.0 ppm                                                              Time     Temp 1   Temp 2   CO out                                                                              NO out NOx out                               Hours: Min.                                                                            (°F.)                                                                           (°F.)                                                                           (ppm) (ppm)  (ppm)                                 ______________________________________                                        :15      132      132      10.28 22.0   23.0                                  :30      353      143      1.22  8.0    8.0                                   :45      351      259      0.45  4.0    4.5                                   1 hour   350      338      0.42  4.0    4.5                                   1:15     349      338      0.43  5.0    5.5                                   1:30     349      338      0.41  6.0    6.5                                   1:45     349      339      0.41  7.0    7.5                                   2 hours  349      339      0.42  8.0    9.0                                   2:15     348      338      0.46  8.5    9.5                                   2:30     349      339      0.45  9.5    10.5                                  2:45     349      339      0.49  10.0   11.5                                  3 hours  349      339      0.48  10.5   12.0                                  3:15     350      340      0.55  11.0   13.0                                  ______________________________________                                    

Experiment No. 2

The conditions for this series of experiments was the same as those forExperiment No. 1. This series was begun with a new catalyst absorber ofthe same type and configuration as described above for Experiment No. 1.

    ______________________________________                                        Initial Starting Pollutant Levels                                             CO in, 10.98 ppm                                                              NO in, 29.0 ppm                                                               NOx in, 33.0 ppm                                                              Time     Temp 1   Temp 2   CO out                                                                              NO out NOx out                               Hours: Min.                                                                            (°F.)                                                                           (°F.)                                                                           (ppm) (ppm)  (ppm)                                 ______________________________________                                        :15      345      225      0.20  2.0    2.0                                   :30      348      308      0.19  2.0    2.5                                   :45      350      315      0.22  2.0    2.0                                   1 hour   350      317      0.24  2.0    2.5                                   1:15     351      317      0.23  2.5    2.5                                   1:30     351      318      0.23  3.0    3.0                                   1:45     351      317      0.24  3.5    4.0                                   2 hours  351      317      0.26  5.0    7.0                                   2:15     350      318      0.24  6.0    8.0                                   2:30     351      319      0.25  8.0    10.0                                  2:45     351      320      0.23  10.0   11.0                                  3 hours  352      320      0.26  10.0   12.0                                  3:15     352      320      0.22  11.0   12.0                                  3:30     353      321      0.26  11.0   13.0                                  ______________________________________                                    

Experiment No. 2-a

The catalyst absorber was regenerated, and the experiment was run againunder the same conditions, using the regenerated catalyst absorber.

    ______________________________________                                        Initial Starting Pollutant Levels                                             CO in, 11 ppm                                                                 NO in, 29 ppm                                                                 NOx in, 33 ppm                                                                Time     Temp 1   Temp 2   CO out                                                                              NO out NOx out                               Hours: Min.                                                                            (°F.)                                                                           (°F.)                                                                           (ppm) (ppm)  (ppm)                                 ______________________________________                                        :15      144      142      7.75  20.0   20.0                                  :30      374      142      0.39  5.0    5.0                                   :45      372      358      0.17  2.0    2.0                                   1 hour   371      362      0.15  1.5    2.0                                   1:15     370      363      0.17  3.0    3.5                                   1:30     370      363      0.17  4.0    4.5                                   1:45     368      361      0.18  4.5    5.0                                   2 hours  367      369      0.13  5.0    6.0                                   2:15     367      360      0.15  6.5    7.5                                   2:30     366      358      0.17  7.5    8.5                                   2:45     366      359      0.18  8.0    9.0                                   3 hours  366      358      0.14  9.0    10.0                                  3:15     366      358      0.17  10.0   11.0                                  3:30     365      358      0.17  10.0   11.5                                  3:45     363      356      0.18  10.5   12.0                                  4 hours  362      354      0.17  11.5   13.0                                  ______________________________________                                    

Experiment No. 2-b

The catalyst absorber was regenerated again, and the experiment was runagain under the same conditions, using the twice regenerated catalystabsorber.

    ______________________________________                                        Initial Starting Pollutant Levels                                             CO in, 11 ppm                                                                 NO in, 29 ppm                                                                 NOx in, 33 ppm                                                                Time     Temp 1   Temp 2   CO out                                                                              NO out NOx out                               Hours: Min.                                                                            (°F.)                                                                           (°F.)                                                                           (ppm) (ppm)  (ppm)                                 ______________________________________                                        :15      186      142      5.53  18.0   18.0                                  :30      276      144      2.65  12.0   13.0                                  :45      275      255      0.85  7.0    7.0                                   1 hour   271      254      0.65  7.0    7.0                                   1:15     267      253      0.77  9.0    9.0                                   1:30     274      255      0.78  10.0   10.0                                  1:45     283      262      0.73  11.0   11.0                                  2 hours  284      266      0.68  11.0   11.5                                  2:15     282      266      0.68  13.0   13.0                                  ______________________________________                                    

Experiment No. 2-c

The catalyst absorber was regenerated again, and the experiment was runagain under the same conditions, using the three time regeneratedcatalyst absorber.

    ______________________________________                                        Initial Starting Pollutant Levels                                             CO in, 9.05 ppm                                                               NO in, 26.0 ppm                                                               NOx in, 32.0 ppm                                                              Time     Temp 1   Temp 2   CO out                                                                              NO out NOx out                               Hours: Min.                                                                            (°F.)                                                                           (°F.)                                                                           (ppm) (ppm)  (ppm)                                 ______________________________________                                        :15      354      142      1.06  7.0    7.0                                   :30      356      150      0.49  2.0    2.0                                   :45      354      338      0.41  2.0    2.0                                   1 hour   351      337      0.43  2.0    3.0                                   1:15     352      338      0.45  3.0    5.0                                   1:30     352      339      0.50  6.0    7.0                                   1:45     352      337      0.50  7.0    8.0                                   2 hours  351      338      0.50  8.0    9.0                                   2:15     350      336      0.49  8.5    9.5                                   2:30     349      335      0.50  9.0    10.0                                  2:45     348      334      0.56  10.0   11.0                                  3 hours  348      334      0.58  11.0   12.0                                  ______________________________________                                    

Experiment 3--First Run

This experiment was run using a monolith core catalyst in a laboratoryset up under the conditions set forth below. The space velocity was10,000 per hour. The initial starting pollutant levels are set out attime zero (0) minutes. Only one catalyst absorber unit was used and thetemperatures was measured just before the catalyst absorber.

    ______________________________________                                        Time      Temp    CO      NOx   NO    Sulfur (SO.sub.2)                       (Minutes) (°F.)                                                                          (ppm)   (ppm) (ppm) (ppm)                                   ______________________________________                                        Input     351     18.0    33.0  29.0  0.5                                     Concentrations                                                                 1        405     0       1.0         0.5                                      2        415             1.0   0.5   0.35                                     5        420             0.75        0.059                                   10        480             0.45        0.004                                   20        401     0       0.4         0                                       32        380             2.4         0.004                                   42        408             2.3         0.007                                   48        360             1.5         0.001                                   50        344             1.85        0.002                                   64        296             5.2   4.2   0.016                                   75        291             8.6   7.1   0.023                                   85        291             9.0         0.037                                   ______________________________________                                    

Experiment 3--Second Run

The catalyst absorber was regenerated, and the experiment was run againunder the same conditions, using the regenerated catalyst absorber.

    ______________________________________                                        Time      Temp    CO      NOx   NO    Sulfur (SO.sub.2)                       (Minutes) (°F.)                                                                          (ppm)   (ppm) (ppm) (ppm)                                   ______________________________________                                        Input             20.0    34.0  31.0  0.51                                    Concentrations                                                                0.5       378     0.1     1.8         0.08                                    1         369     0.1     1.8         0.02                                    2         343     0.1     1.75  1.55  0.32                                    3         326     0.1     1.75  1.6   0.19                                    6         300     0.1     2.0   1.85  0.05                                    10        286     0.1     2.6   2.6   0.025                                   12        284     0.1     3.0         0.021                                   21        287     0.1     5.0         0.021                                   25        288     0.1     6.2   6.2   0.024                                   30        291     0.1     9.0   7.9   0.02                                    47        300     0.1     13.5  12.5  0.05                                    ______________________________________                                    

Experiment No. 4

In the following experiment, the starting gas was obtained from a slipstream from the turbine exhaust from a cogeneration plant turbine, aswith Experiments 1 and 2. The catalyst has the same configuration as inExperiments 1 and 2. The space velocity of the slip stream was 18,000per hour. The temperature for the upstream first basket was 330° F and300° F. for the downstream second basket. All pollutant measurements arein ppm.

    ______________________________________                                        Time         CO      NOx       NO    NO.sub.2                                 (Minutes)    (ppm)   (ppm)     (ppm) (ppm)                                    ______________________________________                                        Input        20.0    33        27    6                                        Concentrations                                                                0            0       1.5       1.5   0                                        .5           0       1.5       1.5   0                                        1.5          0       5         5     10                                       3            0       10        10    0                                        ______________________________________                                    

Apparatus

To apply the catalyst absorber to the continuous reduction of gaseouspollutants in stack gases an apparatus is required. The catalystabsorber is moved into contact with the stack gas and remains thereuntil the outlet levels of carbon monoxide, nitrogen oxides and/orsulfur oxides exceed some specified low concentrations. The catalystabsorber is then moved out contact with the stack gases for regenerationwhile being replaced with fresh or previously regenerated catalystabsorber. The regenerated catalyst absorber is cycled back into contactwith the stack gases in sequence.

The apparatus to apply the catalyst absorber of the present inventioncan be in the form of a wheel or carousel, a portion of which is incontact with the stack gas and a portion of which is outside of contactwith the stack gas. In this case, the catalyst absorber is mounted tothe wheel and moves in and out of the stack gas stream as the wheelrotates.

The apparatus may alternatively be a moving continuous belt with thecatalyst absorber being disposed on the belt. Alternatively, a fluidizedbed of the alumina spheres for of the catalyst absorbed can be locatedin the stack gas stream. In this embodiment a small fraction of thecatalyst absorber, for example, one percent per minute, is continuouslyremoved, regenerated and returned. Any other apparatus could be used toaccomplish the goals specified herein, the choice of such apparatusdepending upon the individual applications.

It would be obvious to a person of ordinary skill in the art that anumber of changes and modifications can be made to the presentlydescribed process, apparatus and methods without departing from thespirit and scope of the present invention. It is contemplated that thepresent invention is encompassed by the claims as presented herein andby all variations thereof coming within the scope of equivalentsaccorded thereto.

What is claimed is:
 1. A material for removing gaseous pollutants fromcombustion exhaust comprising an oxidation catalyst specie selected fromplatinum, palladium, rhodium, cobalt, nickel, iron, copper, molybdenumor combinations thereof disposed on a high surface area support, saidcatalytic component being intimately and entirely coated with anabsorber selected from a hydroxide, carbonate, bicarbonate or mixturethereof of an alkali or alkaline earth or mixtures thereof.
 2. Thematerial of claim 1 wherein the oxidation catalyst specie is platinum.3. The material of claim 1 wherein the oxidation catalyst specieconcentration is 0.05 to 0.6 percent by weight of the material.
 4. Thematerial of claim 3 wherein the oxidation catalyst specie concentrationis 0.1 to 0.4 percent by weight of the material.
 5. The material ofclaim 4 wherein the oxidation catalyst specie concentration is 0.15 to0.3 percent by weight of the material.
 6. The material of claim 1wherein more than one element is used as an oxidation catalyst specieand wherein each of said elements has a concentration in the range of0.05 to 0.6 percent by weight.
 7. The material of claim 1 wherein thehigh surface area support comprises alumina, zirconia, titania,silica ora combination of two or more of these oxides
 8. The material of claim 7wherein the high surface area support comprises alumina.
 9. The materialof claim 1 wherein the surface area of the support is 50 to 350 squaremeters per gram.
 10. The material of claim 9 wherein the surface area ofthe support is 100 to 325 square meters per gram.
 11. The material ofclaim 10 wherein the surface area of the support is 200 to 300 squaremeters per gram.
 12. The material of claim 1 wherein the absorbercomprises an hydroxide compound.
 13. The material of claim 1 wherein theabsorber comprises a bicarbonate compound.
 14. The material of claim 1wherein the absorber comprises a carbonate compound.
 15. The material ofclaim 14 wherein the absorber consists essentially of carbonate.
 16. Thematerial of claim 15 wherein the absorber consists essentially of sodiumcarbonate.
 17. The material of claim 15 wherein the absorber consistsessentially of potassium carbonate.
 18. The material of claim 15 whereinthe absorber is substantially all calcium carbonate.
 19. The materialaccording to claim 15 wherein the absorber consists essentially ofpotassium.
 20. The material of claim 1 wherein the absorber comprisesmixtures of hydroxides and/or bicarbonates and/or carbonated compounds.21. The material of claim 1 wherein the absorber is disposed on saidmaterial at a concentration in the range of 0.5 to 20 percent by weightof the material.
 22. The material of claim 21 wherein the absorberconcentration is 5.0 to 15 percent by weight of the material.
 23. Thematerial of claim 22 wherein the absorber concentration is about 10percent by weight of the material.
 24. The material according to claim 1wherein said high surface area support is coated on a ceramic or metalmatrix structure.
 25. The material according to claim 24 wherein saidceramic or metal matrix structure comprises monolith.
 26. The materialaccording to claim 25 wherein said matrix structure comprises a metalmonolith.
 27. The material according to claim 26 wherein said highsurface area support comprises alumina.
 28. The material according toclaim 27 wherein said oxidation catalyst specie comprises Pt and saidabsorber comprises carbonate.
 29. The material according to claim 1wherein said absorber coating is contiguous to said oxide catalystspecie.
 30. The material according to claim 1 wherein said oxidationcatalyst specie is contiguous to said support.
 31. The material of claim1 wherein the absorber comprises an alkali metal compound.
 32. Thematerial of claim 1 wherein the absorber comprises an alkaline earthmetal compound.
 33. A process of preparing a material for removinggaseous pollutants comprising depositing an oxidation catalyst specieselected from platinum, palladium, rhodium, cobalt, nickel, iron,copper, molybdenum or combination thereof from a solution onto a highsurface area support, drying said support and depositing from a solutionover said oxidation catalyst specie an absorber selected from ahydroxide, carbonate or bicarbonate and mixtures thereof of an alkali oralkaline or mixture thereof and drying the support thereby coating saidoxidation catalyst specie with said absorber.
 34. The process of claim33 where the oxidation catalyst specie is dried after application. 35.The process according to claim 33 wherein said oxidation catalyst speciecomprises platinum.
 36. The process according to claim 35 wherein saidabsorber comprises a carbonate.
 37. The process according to claim 36wherein said absorber comprises an alkali metal carbonate.
 38. Theprocess of claim 33 wherein the oxidation catalyst specie is activatedafter application.
 39. The process of claim 33 wherein the oxidationcatalyst specie is calcined after application and drying.
 40. Theprocess of claim 39 wherein the absorber is applied to the surface ofthe stabilized oxidation catalyst specie from solution containing asolvent and the solvent is then removed.
 41. The process of claim 39wherein the absorber is applied to the surface of the stabilizedoxidation specie from an aqueous solution and dried.
 42. The process ofclaim 39 where the support for the catalyst absorber is a high surfacearea inorganic material in a shape selected from a sphere, solidcylinder, hollow cylinder, star shape and wheel shape.
 43. The processof claim 39 where the high surface area support is coated on a metalmatrix structure.
 44. The process of claim 39 where the high surfacearea support is coated on a ceramic matrix structure.
 45. The process ofclaim 39 where the metal matrix structure is coated with a high surfacearea material and the coating is stabilized by calcining.